This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Perlecan is a major component of heparan sulfate proteoglycans in basement membrane, which is widely expressed in animal bodies. Its expression is dynamically regulated during development and its aberrant expression is linked to many pathological processes, such as diabetes, atherosclerosis, arthritis and cancer. However, it has been poorly understood how the expression of perlecan is properly regulated. Here we show that by affinity purification we were able to obtain two protein complexes that are specifically associated with perlecan mRNA, likely involved in its pre-mRNA splicing. We will examine the purified protein complexes by mass spectrometry and analyze the proteins for their functional significances in both constitutive and alternative splicing. The proposed experiments will provide mechanistic insights into the regulation of constitutive and/or alternative splicing of perlecan pre-mRNA, which will establish a foundation for long-term studies to elucidate the mechanism of alternative splicing in regulating the expression of perlecan.